1. Field of the Invention
This invention relates to a bacterial culture prepared from the intestinal tract of pathogen-free mammalian animals. It also relates to subcultures of such cultures and to methods of using the subcultures to protect livestock from colonization by enteropathogenic bacteria.
2. Description of the Related Art
Enteropathogens, such as Salmonella and Escherichia coli 0157:H7, cause an unacceptably high incidence of morbidity and mortality in humans and may reduce productivity in livestock populations. Gastrointestinal pathogens in humans are typically derived from intestinal contamination of meats that humans consume. At a symposium on Tracking Foodborne Pathogens from Farm to Table: Data Needs to Evaluate Control Groups held in January, 1995, a question asked was "How important are foodborne diseases?" (Tracking Foodborne Pathogens from Farm to Table: Data Needs to Evaluate Control Groups, Washington, D.C., 3-29, 1995). It was stated that in the United States, there are an estimated 6.5 million to 33 million cases of foodborne diseases each year, resulting in up to 9,000 deaths. The USDA Economic Research Service estimates U.S. medical costs and productivity losses for seven foodborne pathogens at $5.6 billion to $9.4 billion annually. Menning estimates that there are over 5 million cases of meat and poultry foodborne diseases in the United States per year and a large percentage is attributable to Salmonella and Campylobacter infections (J. Am. Vet. Med. Assoc., Volume 192, 494-497, 1988). Roberts estimates that each case of salmonellosis costs $700 (Amer. J. Agr. Econ., Volume 71, 468-474, 1989). Based on surveys estimating foodborne disease in other countries, it would not be unreasonable to project that the number of worldwide foodborne diarrheas per year attributable to Salmonella probably exceeds 100 billion with an estimated cost exceeding 25 billion dollars. These pathogens also account for pain, suffering and loss of life. In addition, enteropathogenic bacteria may also cause substantial economic loss through infection of livestock.
Competitive exclusion (CE) techniques are used for decreasing colonization of enteropathogenic bacteria in poultry. Nurmi et al (Nature, Volume 241, 210-211 1973) found that preparations from mature, healthy chickens conferred protection to young chicks, whose microflora had not yet been established, against Salmonella colonization. Administration of undefined CE preparations to chicks speeds the maturation of gut flora in newly-hatched birds and provides a substrate for the natural process of transmission of microflora from the adult hen to its offspring.
Snoeyenbos et al (U.S. Pat. No. 4,335,107, June, 1982) developed a CE micorflora technique for preventing Salmonella colonization by lyophilizing fecal droppings and culturing this preparation anaerobically. Mikola et al (U.S. Pat. No. 4,657,762, April, 1987) used intestinal fecal and cecal contents as a source of CE microflora for preventing Salmonella colonization. Treatment with this type of culture required media to be anaerobic and pH balanced.
Stern et al (U.S. Pat. No. 5,451,400, Sep. 19, 1995) discloses a mucosal CE composition for protection of poultry against colonization by Salmonella and Campylobactor where the mucin layer of prewashed ceca is scraped and the scrapings, kept in an oxygen-free environment, are cultured anaerobically.
Nisbet et al (U.S. Pat. No. 5,478,557; Dec. 26, 1996) disclose a probiotic that can be obtained from a variety of domestic animals, including but not limited to fowl and also equine, porcine and bovine. Nisbet et al disclose that a stable defined probiotic is preferably obtained by continuous culture of a batch culture produced directly from fecal droppings, cecal and/or large intestine contents of the adult target animal. They further disclose that large quantities of the probiotic may be produced by either batch or continuous culture wherein the batch culture is continued until the concentration of acetic acid is greater than or equal to about 20 mM, the concentration of proprionic acid is greater than or equal to about 10 mM and the concentration of butyric plus isobutyric acid is greater than or equal to 15 mM.
Asplund et al (Journal of Applied Bacteriology, Volume 81, 217-223, 1996) report an in vitro model of the procine intestine and its use to show inhibiiton of Yersinia enterocolitica O:3 by pig ileal and caecal microflora. Caeca and distil parts of the small intestine are collected, kept under anaerobic conditions and the contents collected, pooled and cultivated. Caecal and ileal inocula are shown to suppress the growth of cultured Y. enterolitica, with caecal flora somewhat more effective than ileal flora. No in vivo efficacy was reported.
The present invention provides for the first time a composition and a method for reducing in vivo and/or preventing colonization of mammals, especially livestock, by enteropathogenic bacteria.